Shortened afterburner construction for turbine engine

ABSTRACT

An afterburner construction for a turbine engine, such as a turbofan engine, which is foreshortened by using a construction which utilizes swirl flow phenomena to rapidly mix the engine products of combustion and coolant flow, such as fan air, and/or to rapidly accomplish the afterburning combustion process in the afterburner, while maintaining engine performance and structural part integrity.

United States Patent Markowski [54] SHORTENED AFTERBURNER CONSTRUCTIONFOR TURBINE ENGINE [72] Inventor: Stanley J. Markowski, East Hartford,Conn.

[73] Assignee: United Aircraft Corporation, East Hartford, Conn.

[22] Filed: Oct. 26, 1970 [21] Appl. No.: 84,087

[52] 11.8. Cl ..60/39.72 R, 60/39.36, 60/39.69, 60/39.74 R [51] Int. Cl..F02k 3/10 [58] Field of Search...60/261, 39.36, 39.69, 39.72 R,60/39.74 R; 431/173, 350

[56] References Cited UNITED STATES PATENTS 7/1956 Ferri ..60/39.72 R

COMBUSTION INITIATED IN RECIRCULATING FLow/jy BEHIND FLAMEHOLDER NAPPROACH FLow 2 FUEL SPRAY 3 a? DISTRIBUTION f FUEL SPRAY BAR\Q/ [451Oct. 31, 1972 2,977,760 4/1961 Soltau ..60/39.36 3,030,005 4/1962 Nabour..60/261 3,088,281 5/1963 Soltau ..60/39.65 3,245,218 4/1966 Marchant..60/39.74 R 3,299,632 1/1967 Wilde ..60/39.37 3,300,976 1/1967 Coplin..60/39.74 R

Primary ExaminerDoug1as Hart Attorney-Vernon F. l-lauschild [5 7ABSTRACT 46 Claims, 20 Drawing Figures F FROM PILOT- Low v NONVITIZATEDFLow COM BUSTlON PRODUCTS VITIATED GASES NONVITIATED GASES AXIALDOWNSTREAM FLOW FLAME FRONT RADIUS OF CURVATURE OF STREAM LINE PATENTEH0m 3 1 I972 SHEET 1 OF 6 INVENTOR STANLEY J. MARKOWSKI BY M 1 ,L/ J LATTORNEY PATENTED um 31 I972 SHEU 2 OF 6 A/ CHAMBER I I I PATENTED EI973 3.701, 255

SHEET 3 or 6 COMBUSTION PRODUCZTS FROM PILOT-LOW v cOMBuSTIO INITIATEDIN e RECIRCULATING FLOW/Z BEHIND FLAMEHOLDER A V ATED FLOW V 4/HIGHQVZVITIATED GASES Qw SE 'SE NONvITIATED APPROACH FLOW GASES V AXIALDOWNSTREAM FLOW 2 FUEL SPRAY 3/ 1 m; FRONT DISTRIBUTION RADIUS OFCURVATURE OF STREAMLINE P'A'TENTEO B I912 3.701.255

SHEET u (If 6 PATENTED I973 3.701, 255

sum 5 OF 6 COOLANT FLOW SHORTENED AFTERBURNER CONSTRUCTION FOR TURBINEENGINE CROSS-REFERENCES TO RELATED APPLICATIONS This applicationcontains subject matter related to the following two applicationsassigned to the same assignee: (1) Application Ser. No. 84,086, filedconcurrently herewith for Annular Combustion Chamber for DissimilarFluids in Swirling Flow Relationship and (2) Application Ser. No.84,088, filed concurrently herewith for Combustion Chamber HavingSwirling Flow.

BACKGROUND OF THE INVENTION 1. Field of Invention This invention relatesto afterburner construction and more particularly to the constructionforan afterburner which is intended for use with a turbojet engine,possibly a turbofan engine, so as to shorten the axial length of theafterburner, thereby reducing engine length and weight.

2. Description of the Prior Art In the prior art, attempts have beenmade to more rapidly mix the products of engine combustion and theturbofan air upon entering an afterburner, such as Howald US. Pat. No.3,048,376 and Pierce US. Pat. No. 2,978,865, however, these patentsprovided tortuous, narrow passages through which the exhaust gas and thefan air must pass and this created substantial losses in the system withattendant engine thrust reduction.

Other patents, such as Ferri et al. US. Pat. No. 2,755,623, havesuggested the use of circumferentially rotating flow in combustionchambers to permit the accomplishment of combustion in a shorter axialdistance, however, they do not suggest the use of swirling flowprinciples to accelerate the mixing between two thermodynamically andaerodynamically dissimilar fluids.

In my invention, swirling fluid flow principles are used in a vanecascade in the afterburner to serve the function of accelerating themixing and combustion in the combustion zone of the afterburner and alsothe function of straightening flow prior to discharge of the exhaustnozzle. These afterburner vanes have cooling provisions and may be usedwith many forms of fuel injection and fuel ignition systems.

SUMMARY OF THE INVENTION A primary object of the present invention is toprovide an afterburner of minimal axial dimension or length.

It is an important feature of this invention to reduce the length of anafterburner by passing swirling air therethrough and between at leastone cascade of selectively contoured vanes which are positionedcircumferentially about the afterburner chamber and which serve ascombustors when fuel is injected into the air at a station upstreamthereof to form a fuel-air mixture which is ignited with flameholdersupport at the side of the vane defined passage having the greaterradius of curvature to thereby perform the afterburning function and theflow straightening function in the combustors defined between the vanes.

A further feature of this construction is that numerous fuel injectionmechanisms, flameholder mechanisms and interface disturbing triggermechanisms can be used therewithand the construction includes provisionsfor keeping the vane walls cool.

' It is a further object of the present invention to teach apparatus toshorten the length of an afterburner utilizing swirl flow by placing acascade of flow straightening vanes'about the periphery of theafterburner and positioning aerodynamic flameholders I immediatelyupstream or at the leading edge thereof and 'interdigitated with respectthereto to establish a pilot combustion zone for the fuel-air mixturebeing passed through the vane cascade for curved flow combustion withinthe cascade.

It is a further object of this invention to teach apparatus forshortening an afterburner by utilizing circumferentially positioned andradiallydirected vanes to form a vane cascade, in combination withflameholder and fuel injection mechanism to define pilot combustorsbetween the vanes, and wherein the vanes are hollow and includeprovisions for cooling the vane wall, in particular the substantiallydownstream directed concave vanewall in installations where structuralpart cooling is necessary.

It is a further teaching of this invention to utilize either aconcentric mixer or a barberpole mixer upstream of my cascadeflameholder inan annular combustion chamber. While the cascadeflameholder can be used in a turbojet engine, in a duct heater engine,and in turbofan engines, it is particularly attractive when used with amixed turbofan cycle engine because a concentric or barberpole mixer canbe utilized forward of the cascade flameholder-to mix the fanand enginestreams and provide this mixture to'the cascade-in the proper swirl flowrelationship,"so that accelerated mixing and combustion will take placewithin the cascade simultaneously with the cascade performing thefunction of straightening the'direction of fluid flow to an axialdirection.

In accordance with one of the features of'th'e'present invention, theengine exhaust gas and the turbofan air entering the afterburner arecontrolled by means of guide vanes or the like so that as they enter theafterburner through a concentric mixer, the product parameter p, V ofthe engine exhaust gases is greater than the product parameter p V ofthe fan air where p is density and V, is tangential velocity, andfurther wherein trigger means are provided to physically disturb theinterface between the swirling streams of engine exhaust gas and fan airentering the afterburner, and still further wherein the afterburner mayinclude a variable area exhaust nozzle at the downstream end thereof andflow straightening vanes upstream of the exhaust nozzle, and stillfurther wherein said trigger means may be circumferentially oriented andradially extending corrugations or convolutions and/or axially extendingscallops attached to the downstream end of the splitter duct between theengine exhaust gases and the fan air. v

In accordance with still a further feature of the present invention, thefan air and the engine exhaust gas of a turbofan engine are mixedrapidly before or upon entering the afterburner in a construction whichutilizes a plurality of circumferentially positioned and helicallyoriented three-dimensional scoop cascades which intercept and deliverfan air through a plurality of circumferentially positioned andhelically oriented matching slots in a splitter duct extending acrossthe fan air stream, .and wherein the areaof the duct system throughwhich the engine exhaust gases enter the afterburner has a selectedrelationship to the total slot area so as to control the fan airvelocity magnitude entering the afterburner chamber and so that thescoop and slot shape establishes a plurality of circumferentiallyoriented and selectively spaced helical sheets of fan air penetratingand mixing with the swirling engine products of combustion in a minimalaxial distance and with minimal mixing losses.

Other objects and advantages of the present invention may be seen byreferring to the following description and claims, read in conjunctionwith the accompanying drawings.

DESCRIPTION OF THE DRAWINGS flameholder is a pivotable door attached tothe leading edge of the turning vanes.

FIG. 4 is a showing similar to FIG. '3 of a modification of my cascadeflameholder.

FIG. 5 is an enlarged, perspective showing of the flameholder mechanismused in the FIG. 4 construction.

FIG. 6 is a perspective showing of the FIGS. 4-5 flameholder mechanismsin their afterburning positions and connected by a flamespreader.

FIG. 7 is a cross-sectional showing of the inlet portion of anafterburner utilizing my combustion chamber defining and flow turningvanes in combination with an aerodynamic flameholder to form a cascadeflameholder.

FIG. 8 is a view taken along line 8-8 of FIG. 7.

FIG. 9 is an enlarged cross-sectional showing of my aerodynamicflameholder.

FIG. 10 is a cross-sectional showing of an afterburner utilizing aflameholder and vane construction generally of the type shown in FIG. 2but wherein the vanes are hollow and have cooling provisions.

FIG. 11 is an enlarged showing of one of the hollow vanes of the FIG. 10construction.

FIG. 12 is a view taken along line 12-12 of FIG. 11.

FIG. 13 is a view taken along line l3-13 of FIG. 11.

FIG. 14 is a cross-sectional showing of an afterburner with a centralportion thereof removed to illustrate the use of the fan air duct andthe splitter duct as concentric mixers alone or with a cascadeflameholder.

FIG. 15 is a view taken along line- 15-15 of FIG. 2 and showing radiallyextending corrugations as trigger means on the splitter duct.

FIG. 16 is an alternate form of trigger means and is illustrated asaxially extending scallops at the trailing end of the splitter duct. I

FIG. 17 is an illustration of one of the vane cascades of the FIG. 14construction shown in variable positionable form.

FIG. 18 is a partial showing of the afterburner inlet utilizing abarberpole mixer.

FIG. 19 is an unrolled showing of the tapered separator duct whichextends across the fan-air passage to illustrate the helical slotplurality used therein and to illustrate also the three-dimensionalhooded, vaned cascade used with these slots.

FIG. 20 is an alternate form of the tapered separator duct and the vanedcascade and slot combination of the barber-pole mixer.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 we seeturbine engine 10, which is shown to be of the turbofan variety purelyfor the purpose of illustration but it should be noted that theinvention disclosed herein would have application to any engine in whichengine exhaust gas were discharged into an afterburner, preferably incombination with coolant gas. Engine 10 is generally of circularcross-section and concentric about axis 12 and includes fan section 14,compressor section 16, burner section 20, and turbine section 22, andafterburner section 24. Variable area exhaust nozzle 26 is preferablylocated at the downstream end of the afterburner to vary outlet area inconventional fashion. Fan duct 28 is of circular cross-section andpositioned concentrically about axis 12 and connects to afterburner duct30 so as to conduct the fan air directly into the afterburner. Enginecasing 32 is positioned concentrically within fan duct 28 and cooperatestherewith to define annular fan air passage 34 and envelops the enginecompressor section 16, burner section 20and turbine section 22 andculminates in or attaches to splitter duct 36, which envelops the laststage 38 of turbine section 22 and projects into or toward theafterburner chamber 40 formed within afterburner duct 30. Fan air duct28 and splitter duct or engine exhaust duct 36 form concentric mixer 41.Fan air after passing through annular passage 34 flows radiallyoutwardly of splitter duct 36 and engine exhaust gas flowing throughpassage 42, defined within splitter duct 36, flows radially inwardly ofsplitter duct 36, and since both of these fluids will be flowing inswirling fashion either due to the action of the engine includingturbine stage 38 and the action of the blades of the fan section 14, oradditional flow directing vanes utilized therewith, an interface 44 willbe established between these two swirling fluid streams downstream ofsplitter duct 36. To establish the desired swirling flow, it may bedesirable to remove or adjust the conventional flow straightening vanesdownstream of the turbine and the fan.

In the afterburner section 24, fixed inner body 46 is positionedconcentrically within afterburner duct 30 and vane cascade 48, whoseconstruction and function will be described in greater particularityhereinafter, extends between afterburner duct 30 and fixed inner body46. Fuel injection means 50 injects fuel upstream or forward of vanecascade 48 into the fan air exhaust gas mixture to form a fuel-gasmixture therewith. Ignitor means (not shown) of conventional designwould be used to initiate combustion in combustion zone 58.

In operation, the products of combustion enter the afterburner throughpassage 42 and intermix with the fan air which enters the afterburnerthrough passage 34. Fuel is injected by injector 50 and combustion takesplace in the combustion zone 58 and 40 and the products of combustionthereof, in a vitiated state, are then discharged to atmosphere throughvariable area exhaust nozzle 26 to perform a thrust generating function.

It is an important feature of my invention to shorten the afterburnercombustion zone proper by utilizing a cascade flameholder of theconstructions shown in FIGS. 2-13, and this cascade flameholder may beused with or independently of the mixer configurations shown in FIGS.14-20 if the engine is a turbofan cycle.

Referring to FIGS. 2 and 3 we see afterburner chamber 40 defined withinafterburner duct 30 and with variable area exhaust nozzle 26 at thedownstream end thereof. If required, afterburner duct will include acooling liner 90 of cylindrical shape and concentric about axis 12 whichdefines a cooling air annular passage 92 with duct 30. Cooling liner 90performs the function of distributing the available cooling airselectively over the entire length of the afterburner and usesconventional means, such as louvers or transpiration cooling, to performthis function. Vane cascade flameholder 48 consists of a plurality ofradially extending and circumferentially oriented vanes 94 withflameholder member 96 utilized therewith. As previously described, fuelinjection mechanism 50 are shown as radial spray bars in FIGS. 2 and 3and inject atomized fuel into combustion chamber 40 to be carried withthe swirling gas through the vane cascade flameholder 48 for mixing andcombusting therewithin. The vane cascade and the flameholders 96preferably extend radially across annular passage 43 defined betweeninner body 46 and the afterburner outer case 30 or liner 90 andconstitute a circumferential row or cascade of vanes. These vanes areshown in greater particularity in FIG. 3 wherein it will be noted thatadjacent vanes 94 define passage 110 therebetween and the vanes are soshaped that the inlet or upstream portion 112 of passage 110 opens inthe direction of the swirling approach flow V, while the downstreamportion 114 of passage 110 extends in the direction of axis 12 so thatvanes 94 serve as straightening vanes as well as forming combustorstherebetween as soon to be described. Passage 110 is defined betweenconcave wall 116 of one of the vanes 94 and convex wall 118 of theadjacent vane 94 so that these walls become the walls of passage 110. Itwill be noted that flameholder mechanism 96 is a extending plate memberwhich preferably extends for the full radial dimension of vanes 94 andis pivotally attached to vane 94 at its leading edge at pivot station126 so that by any convenient means, such as the construction shown inFIG. 17 to be described hereinafter, the flameholder plate member 96 maybe pivoted between the FIG. 3 solid lines, afterburning positions wherethey cooperatewith vanes 94 to form recirculation zone 128 and aretracted nonafterburner position in which they lay flat against orrecess into the concave surface 116 of vanes 94 so as to present minimumdrag during nonafterburning operation. Flameholder members 96 include aplurality of apertures 148 extending therethrough in a radiallyextending row or pattern so as to permit the fuel-air mixture to passtherethrough into recirculation zone downstream thereof for ignition andburning in zone 125 to form a pilot combustion zone, and the remainderof the fuel-air mixture passing through passages 110. It will be notedthat the hot combustion gases 128 from the pilot 127 flow along theconcave side of passage 110 parallel to the flow of the nonvitiatedfuel-air mixture and serves to ignite the fuel-air mixture.

In operation, the fuel-air mixture formed by the plurality of fuel spraybars 50 injecting into the passing air, enters passage 110 at inletsection 112 in the downstream direction of flow V. It may be consideredthat vanes 94 are curved about center of curvature and that due to theswirling motion of the fuel-air mix-v ture about axis 12 as it enterschamber 110 and the subsequent straightening of the flow as itprogresses through passage 110, it is evident that the flow isconstrained by the vanes 94 to follow a curved path in the plane of FIG.3. Furthermore, an interface 44 is established in this curved passagebetween the hot combustion products 128 from the pilot burner 127 andthe nonvitiated, cool, fuel-air mixture flowing through the remainder ofthe passage as shown in FIG. 3. Since the pilot gases are at aconsiderably higher temperature and have experienced the lossesassociated with passing through the flameholder holes and combustion,the pV, product of these gases is less than that of the nonvitiatedflow. As my copending US Pat. application filed on even date andentitled Annular Combustion Chamber for Dissimilar Fluids in SwirlingFlow Relationship fully explains, whenever two fluids flow parallel to acurved interface in such a way that the product parameter pV, of thefluid at a smaller radius is greater than the product parameter pV, ofthe fluid on the larger radius side of the interface, where V, refers tothat component of the gas velocity in the tangential direction relativeto the center of curvature of the interface, the interface will beunstable and rapid mixing will occur. Such is the case in passage 110and this product parameter inequality accelerates not only mixingbetween the cooler fuel-air mixture and the products of combustion butburning of the nonvitiated fuel-air mixture due to this rapid mixing.Even if combustion is not completed in cascade 48 the interdigitatedradially extending sheets of hot gas and cooler fuel-air mixture in theduct downstream of vanes 94 will promote completion of the combustionwithin a short distance downstream of vanes 94. This vitiated mixture isthen discharged through outlet portion 114 in the direction of axis 12as nonswirling flow to be discharged in this fashion to generate thrustthrough the variable area exhaust nozzle 26.

In the FIG. 3 construction, three fuel spray bars 50 are shownpositioned between adjacent vanes 94 and at one of the stations aredesignated number 1, 2, and 3 for identification. For power controlpurposes, the fuel spray bars 1, 2, and 3 can be progressively flowed inresponse to increased engine power requirements. For example, spray bar1 would be used at all times during low power afterburner operation andpossibly also to maintain pilot combustion zone 128 ignited at all timesunder circumstances where immediate power increase might be required. Inresponse to demand for increased power, spray bar 2 would be flowedalong with spray bar 1 for intermediate afterburner operation, and inresponse to a demand for maximum power, spray bars 1, 2 and 3 would beflow simultaneously. I

A modification of my cascade flameholder 48 is shown in FIG. 4 wherein.vanes 94 form passages 110 as in the FIG. 3 construction. It will benoted that flameholder mechanism 96 is a radially extending member ofairfoil cross-section which is located at the inlet portion 112 ofpassage 110 and is selectively positioned from vanes 94 to form meteringslot 120 therebetween through which a selected amount of cooling air isdirected against the concave surface 116 of vane 94 for coolingpurposes.

Flameholder 96 is shown in greater particularity in FIG. and is ofgenerally airfoil cross-section and includes stationary member 122 andpivotable door member 124 pivotally attached thereto along radiallyextending hinge 126. Door member 124 is-pivotable, and may be actuatedas shown in FIG. 17, between its FIG. 5 position, which is itsnonafterburning position, wherein the door member 124 cooperates withthe fixed portion 122 of flameholder member 96 to define a smooth,aerodynamic, low drag shape. As best shown in FIG. 6, door members arepivotable to an open or afterburning position so as to cooperate withfixed portion 122 in defining a void cavity 128 therebetween. Fuel-airmixture enters this cavity through holes 148 in door 124. Conventionalignition means, such as spark plug 130 shown in FIG. 6, can be used toignite the fuelair mixture in the pilot combustion zone 128 and it ispreferable that flamespreader 132, which is preferably a trough shapedring, extend circumferentially about axis 12 such that its hollowinterior 134 is in communication with the hollow interiors 136. offlameholder 96 so as to assist in initiating combustion and spreading itto the various radial pilot flameholders 96.

While the fuel injection means shown in FIGS. 2 and 3 is a plurality offuel spray bars, it will be noted by viewing FIG. 4 that the fuelinjection means can well be a plurality of radially extending conduits160 located in the vane forward or upstream portion at convex surface 118 and including a radially extending hole pattern 168 through whichfuel is injected for mixing with the air entering passage 110. Inaddition to these two types of fuel injection, as best shown in FIG. 5,the fuel injection means can be a similar conduit member 166 extendingradially through the fixed portion 122 of flameholder 96 and includes anaperture pattern 168 communicating with passage 166 and passage 110through which atomized fuel is sprayed. The recessed flameholders 160and 166 have an advantage over spray bars 50, in that they create nodrag.

Except for the different flameholder construction, the operation of thecascade flameholder 48 shown in FIGS. 4 and 5 is as previously describedin connection with the FIG. 3 construction.

In any of these constructions, it may be desirable to provide triggermeans to physically disturb the interface between the swirling, cooler,fuel-air mixture and V the swirling, hot products of combustion andtrigger means may comprise physical projections 150, shown in FIGS. 5and 6 extending from the outer periphery of door member 124. To providea smooth, low-drag, airfoil shape during the nonafterburning mode ofoperation, indentures 154 may be provided in the trailing edge 152 ofstationary portion 122 of flameholder 96 to receive trigger projections150 in nested relationship.

Another variation of cascade burning which may be used in myforeshortened afterburner to accelerate combustion is shown in FIGS.7-9. Preferably, this configuration and the previously describedconfiguration may. be used at the very forward end of the afterburnerchamber 40 downstream of a diffuser section 170 formed betweenafterburner duct 30 and tapered inner body 46. The diffuser actionserves to reduce the axial component of the swirling flow velocity, V,but does not retard substantially the tangential flow velocity V,. Thisaids in supporting combustion and reduces the pressure loss associatedwith the combustion process. In this modification, straightening vanes94 are again used as in the FIG. 2-4 constructions to receive theswirling fuel-air mixture approaching indirection V and to straightenthe flow thereof to be in alignment with axis 12. However, a differentflameholder and fuel injection provision is included in the FIG. 7-9embodiment.'In this embodiment, the flameholders 172 are of theaerodynamic type and comprise a hollow airfoil shaped tube 174, shownbest in FIG. 9, which extends substantially radially with respect toaxis 12 and which is interdigitated between adjacent turning vanes 94 sothat the wake 128 therefrom flows along concave surface 116 of vanes 94and passages 110. Aerodynamic flameholders 172 include a pattern oflateral apertures 176 on at least one side, and preferably both sidesthereof toward the trailing edge 178 thereof. In this construction, hotair in some form and fuel are injected into the hollow interior 180 ofaerodynamic flameholder 172 to be injected substantially laterallythereto through laterally directed slot patterns 176 at sufficientvelocity to disturb the flow passing the vane and create a widerecirculation zone 12S downstream of each aerodynamic flameholder toserve as a pilot flame for the fuel-air mixture which is being passedthrough passages 110 by the injection of fuel in any conventional mannersuch as the fuel spray bars 50 of the type disclosed in FIG. 2. The warmair for this fuelair mixture may be tapped through line 182 fromupstream of the last turbine stage 22 and fuel is added thereto from afuel source through line 184 with valves 186 and 188 determining therichness of the fuel-air mixture. This mixture is made excessively richso that it will not burn until the mixture is diluted by mixing with theflow in the afterburner duct after which it will spontaneously ignite,burn and provide an ignition source for the fuel-air mixture from fuelspray bars 50 entering passages 110. Accordingly, accelerated mixing andburning takes place in combustor passages due to the aforementionedproduct parameter difference which occurs between the products ofcombustion and the nonvitiated fuel-air mixture passing throughcombustor passage in swirl flow relationship. Again, in thisconstruction, an irregular aperture pattern of apertures 176 orselectively positioned indentations or bulges, such as element in FIG.5, in the trailing edge 178 of aerodynamic flameholder 172 will serve astriggering means to physically disturb the interface between theproducts of combustion and the nonvitiated fuel-air mixture to furtheraccelerate mixing therebetween.

In certain installations it is important to keep all parts which areexposed to the atmosphere operating at a relatively reduced temperatureand this can be accomplished in my turning vane combustor configuration48 as best shown in the FIG. -13 modifications the cooling technique nowto be described is important to structural cooling, especially inafterburner installations. As best shown in FIGS. 10-13, vanes 94 arehollow in construction and have flow turning vane cascade 180 at theirouter edges which intercept the fan air and further include cooling airdischarge slots, such as slot 182 at a low static pressure region closerto centerline 12 and toward the vane upstream stations. In a turbojetinstallation, cooling air would preferably be ducted to the vanes 90from the compressor or elsewhere. Centerbody 46 may also be hollow andthe interior of vane 94 is in communication with the hollow interiorthereof such that coolant discharge may occur through slots 184 in thehollow afterbody 46, preferably as far upstream as possible to achievemaximum pressure differential between the inlet to vanes 94 and thedischarge slots. The FIG. 10-13 constructions can be generally of thetype shown in connection with FIGS. 3- 9 but the details of the vanes 94are different to accommodate cooling. In this construction, it isdesirable that vanes 94 overlap circumferentially. As best shown in FIG.11, the fan air enters hollow vane 94 through flow turning vane cascade180 which is positioned to intercept fan air. Upon entering the vane,the cooling air will flow directly to either or both discharge slots 182and 184 or, if selective cooling is desired as to favor concave surface1 16, which is exposed in a downstream location and experiences a higherheat load during augmented operation, the hollow interior of the vane 94is compartmentized as best shown in FIGS. 11-13. In this compartmentizedconstruction, the fan air, after passing through turning vane cascade180, enters inlet manifold 190 at the radial outer vane location.Separator member 192 extends between the vane leading edge 194 and thevane trailing edge 196 to separate the flow entering inlet manifold 190into a first hollow compartment 198 which includes convex wall 118 asone of its boundary defining walls and the remainder of the air frommanifold 190 enters second compartment 200 which is of Finwallconstruction.

As best shown in FIG. 13, the inlet manifold 190 is divided by separator192 so that the bulk of the air entering the vane 94 is directed intoFinwall passage 200, while the lesser portion passes through hollowpassage 198. The Finwall construction is best shown in FIG. 12 andincludes spaced walls 116 and 202 which have radially directedcorrugated sheets 204 therebetween. This Finwall construction provideslarge extended surfaces for the cooling air to scrub against and removeheat from concave wall 116 of the hollow vane to perform a maximumcooling function with respect thereto. After passing through passages198 and 200, the coolant is then received in discharge manifold 206,which is hollow and runs throughout the full vane axial dimension and isdischarged therefrom either through a plurality of slots 182 at an innerradial station in the vanes or enters hollow inner body 46 for dischargetherefrom through slots 184, or both. Coolant flow is insured in thisfashion since in the swirling flow approaching the vanes the staticpressure increases with the distance from axis 12 and therefore slots182 and 184 are located at minimal static pressure stations while inletis at a point of maximum static pressure and the radial pressuregradient across the swirling flow provides the pressure differential toflow the cooling system.

While the FIG. 10-13 construction is shown in a turbofan engineenvironment, it should be borne in mind that hollow, cooling vanes inthis cascade flameholder construction could be used in many differentkinds of engines. For example, the FIG. 10-13 cascade flameholder couldbe used in a duct heater within the fan duct of a turbofan engine or inan unmixed turbofan engine where unmixed fan air provides the coolingair. In other engine applications, such asa turbojet engine, the coolingair could be piped to the vane interior from the engine compressor orother convenient pressure source.

As best shown in FIG. 1, the configurations of FIGS. 2-13 may be used toform the combustion zone of an afterburner.

In turbofan engines, higher nonaugr'nented (without afterburning) thrustis achieved when the fan stream and the engine exhaust gas stream aremixed and discharged through a common exhaust nozzle to generate thrust.To reduce the overallengine length and weight, it is desirable toreduce'the afterburner length by accelerating this mixing. Mixingacceleration can be achieved by the use of concentric or barberpolemixers now to be described. These mixers not only reduce afterburnerlength and weight but are well suited for use with the previouslydescribed cascade burner 48 because the exit flow therefrom is swirlingand swirling inlet flow is a requirementof the cascade flameholder.

A concentric mixer used in this environment is shown pFIGS. 14-16 and itshould be noted that the mixer is located upstream of the previouslydescribed cascade flameholder 48.

Referring to FIG. 14 we see that fan air enters afterburner chamber 40through annular passage 34 and the engine gases enter the afterburnerchamber 40 through annular passage 42 to establish therebetween. Both ofthese streams may be swirling about axis 12 without further assistance,or by the removal of the flow vanes which are conventionally locateddownstream of the fan and turbine, however, it may be desirable to placea cascade of turning vanes 60 in passage 34 and a cascade of turningvanes 62 in passage 36 to establish the desired tangential velocities, Vof the swirling streams to accelerate mixing between the engine exhaustgases and the fan air by establishing the mixing criteria productparameter ratio p V p V where p and V are the density and tangentialvelocity of the engine exhaust gas, respectively, and p and V are thedensity and tangential velocity of the fan air, respectively. The theoryof swirling flow intermixing is explained in detail in my copendingapplication filed on even date and entitled Annular Combustion Chamberfor Dissimilar Fluids in Swirling Flow Relationship, to which referencemay interface 44 be made. With this product parameter ratio established,interface 44 is unstable and intermixing between the engine exhaust gasand the fan air is accelerated. To further accelerate this intermixing,radially extending corrugations 66 may be positioned in the splitterduct 36 at its downstream end. These convolutions physically disturb theunstable interface 44 to further accelerate the rate of intermixingbetween the engine exhaust gas and the fan air. So as to hold flow losesto a minimum while accomplishing the desired perturbation of theinterface, it is important that convolutions 66 extend over about to 30percent of the fan air and engine gas streams.

In addition to, or as a substitute for, the radially extendingcorrugations shown in FIG. 15, splitter duct 36 could be fabricated toinclude axially extending scallops 68 shown in FIG. 16 which will serveto physically disturb the unstable interface 44. Because it is desirableto cause the exhaust gases to be discharged to atmosphere throughexhaust nozzle 26 in an axial flow direction, it may be desirable toplace a cascade of straightening vanes 70 in the afterburner chamber 40upstream of the exhaust nozzle. Obviously, these vanes could be thepreviously discussed flameholder vanes.

While the vanes of cascades 60 and 62 may be selectively shaped andoriented and fixed in position, it may be desirable to make one or bothof them of the variable position type as shown in FIG. 17. In the FIG.17 construction, vane 60 is pivotally connected to afterburner duct 30and splitter duct 36 by pivot pin members 72 and 73 which extends fromopposite ends thereof. Each vane 60 carries ring gear 75 at its outerend. Annular ring gear 78 is supported for rotation about axis 12 bysupport ring 80 and has matching gears matingly engaging the gears ofeach of the ring gears 75 so that as annular gear 78 is caused to rotateabout axis 12 by pilot manipulation in any convenient way, such as pilotcontrolled linkage 82 which connects pivotally to annular gear 78'and ispivotally supported about pivot point 84, each of the ring gears 75 andhence vanes 60 are caused to pivot about their axis in unison to a newposition so as to vary the flow angle and hence the tangential velocityV, of the fluid flowing between the vanes.

Another modification of the accelerated interrnixing feature of myafterburner is shown in FIGS. 18 and 20. As best shown in FIG. 18,conical separator duct 70 is connected at its forward end to engine case32 and increases in radial dimension from axis 12 in a downstreamdirection and attaches at its downstream end to fan case 28 so as toextend completely across the fan air passage 34. FIG. 19 shows conicalseparator member 70 in an unrolled condition'and it will be noted thatit includes a circumferentially extending row of slots 72, which slotsare helically oriented with respect to axis 12 and of selective spacingand numbering that the total area defined by the slot plurality throughwhich the fan air must pass is matched to the cross-sectional area ofannular passage 42 downstream of turbine stage 38 through which theengine exhaust gases must pass so as to establish a selected velocitymagnitude V at which the fan air enters the afterburner chamber 40through slots 72. Three-dimensional scooped cascades 74 extend from eachslot and include hood member 76 which connects to separator 70 at itsafter end and is open at its forward end to intercept fan air, and whichfurther includes a cascade of turning vanes such as 78 which cooperatewith hood member 76 in intercepting the fan air from passage 34 andcause the fan air to turn in direction smoothly into the afterburnerchamber 40 through slots 72 at a selected tangential velocity V,. Thisconstruction is known as barberpole mixer 71 in that swirling helicalsheets of fan air are caused to penetrate into the swirling engineexhaust gases due to the action of the three dimensional vaned cascadesand slots 72 to establish interdigitated streams of dissimilar fluidsfor accelerated mixing therebetween. The connecting of vaned cascades 74and slots 72 is selected so as to establish the mixing criteria productparameter ratio pV, (engine exhaust gases) VF (fan air) where p is fluiddensity and V, is fluid tangential velocity.

For ease of construction, it may be desirable to fabricate separator 70as shown in FIG. 20 so that it includes stepped forward ends 96 in wallmembers 98, which cooperate with hood members 100 to intercept anddirect the flow of fan air into the afterburner with the cooperation ofthe cascade of vanes 102. In the FIG. 20 construction, the vanes areattached by welding or other convenient means to the stepped front end96 of the wall members 98 and to hood member 100 to form the selectivelyshaped passage 104 therethrough to determine the tangential velocity V,at which the fan air is going to enter the helically directed, spacedslots 72. As such, FIG. 20 represents a barberpole mixer modificationwhich may be simpler to fabricate.

It will be noted that in both the concentric mixer configuration shownin FIGS. 14-16 and in the barberpole mixer configuration shown in FIGS.18 and 19 a swirling flow situation is created within the afterburnerpassage 40 and this swirling flow condition is a requirement for theinlet flow of the cascade flameholder 48 previously described inconnection with FIGS. 2-13. Accordingly, as best shown in FIG. 14, it ishighly desirable to utilize either of these mixers upstream of cascadeflameholder 48 to accomplish overall afterbumer length reduction.

While I have illustrated and described my cascade flameholder 48 in anafterbumer environment as shown in FIGS. 2-13, it is important to notethat it has several additional applications. For example, in theturbofan engine illustrated, the cascade flameholder 48 is shown to beused in the mixed-flow afterburner, but it could also be used as a ductheater by being selectively positioned in passage 34. My cascadeflameholder could also be used in the main combustion chamber or theafterburner of a turbojet engine, or could, in fact, be used as aninterburner between turbine stages, or in any other environment whichdefines an annular passage in which a change in the flow directions isdesirable. The vanes of my cascade flameholder act as straighteningvanes in both the burning and nonburning modes of operation and alsoserve as combustion flameholders.

It will be evident to those skilled in the art that an afterburner of myconstruction is foreshortened by the use of either the concentric mixeror the barberpole mixer with the vane cascade combustors taught hereinand an advantage to a lesser degree will also be achieved by using themixers or the vane combustors by themselves.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

Iclaim:

1. An afterburner having:

A. an afterburner duct having an axis and defining an afterburnerchamber therewithin,

B. means to pass fluid through said afterburner chamber in a swirlingflow pattern,

C. a cascade of radially extending, airfoil shaped vanes each having aconvex side and concave side, said vane positioned concentrically aboutsaid axis within said afterburner chamber with the vanes shaped so thatadjacent vanes define a passage therebetween which has an upstreamportion which defines a passage which is in substantial alignment withthe direction of fluid flow passing through the afterburner chamber andwhich has a downstream portion which defines a passage substantially inalignment with the axis so that the vanes serve as straightening vanesfor the fluid flowing therebetween, and so that the concave side andconvex side of adjacent vanes form concave and convex walls of saidpassage, respectively,

D. a radially extending flameholder member positioned at each passageupstream portion adjacent the passage concave wall so as to establish astagnation zone downstream thereof in said passage adjacent said concavewall,

E. means to pass fuel into said passage to form a fuelfluid mixturepassing over said flameholder,

F. means to ignite said fuel-fluid mixture to establish combustion insaid zone within said passage adjacent said concave wall to establishoutside-inside burning within said passage progressing in the directionfrom the concave wall to the convex wall.

2. Apparatus according to claim 1 wherein said flameholder member is ofgenerally airfoil cross-section and includes a pivotable door memberattached to the side thereof away from said passage concave wall andpivotable between a first non-afterburning position wherein itcooperates with the remainder of the flameholder member to define anairfoil cross-section and a second, afterburning position where itextends into the passage to increase the size of the stagnation zone.

3. Apparatus according to claim 2 wherein said door member isperforated.

4. Apparatus according to claim 3 and including trigger means located onsaid door member to physically disturb the interface between theproducts of combustion of the stagnation zone and the fuelfluid mixture.

5. Apparatus according to claim 1 wherein said fuel injection meanscomprises a plurality of radially extending spray bars located in saidafterburner chamber tending radially in each vane and including aradially extending pattern of apertures opening into said passagethrough said concave wall.

8. Apparatus according to claim 1 and including flamespreader meansinterconnecting said flameholder means.

9. Apparatus according to claim 1 and including diffuser means upstreamof said flameholder and vanes in said afterburner chamber to reduce theaxial velocity but not the spin velocity of the swirling fluid passingthrough the afterburner chamber.

10. Apparatus according to claim 1 wherein said flameholder means isspaced from said convex wall so that a cooling fuel-fluid mixture passestherealong and is positioned in closely spaced relation to said concavewall so that cooling fuel-fluid mixture is metered therebetween to passat high velocity along said concave wall.

1 1. An afterburner having an axis and including:

A. an afterburner case concentric about the axis, and

defining an afterburner chamber therewithin,

B. a plurality of radially directed, circumferentially oriented vaneseach having a convex side and concave side, said vanes forming a vanecascade extending across at least a part of said afterburner chamber,wherein said vanes are airfoil shaped such that adjacent vanes define apassage and combustor therebetween with the concave side of one vaneforming a concave wall of the passage and the convex side of theadjacent vane forming a convex wall of the passage, and such vanes beingselectively shaped so as to define the inlet portion of said passage toextend substantially in the direction of intended fluid flow and theoutlet portion of passage extending substantially along said axis,

C. a radially extending flameholder of airfoil crosssection positionedadjacent but in spaced relationship to the concave wall of said passageat the inlet portion thereof to define a metering passage for coolingfluid between said flameholder and said concave wall,

D. means to pass fluid through said afterburner,

E. means to inject fuel into said fluid upstream of said passage,

F. means to ignite said fuel-fluid mixture downstream of saidflameholders to establish pilot combustion in the stagnation zone formeddownstream thereof so that the products of combustion have a density,p,, and a tangential velocity V and so that the unvitiated fuel-fluidmixture has a density, p and tangential velocity V to establish theproduct parameter ratio p V,, p V to thereby accelerate intermixing andcombustion between'the unvitiated fuel-fluid mixture and the pilotproducts of combustion.

12. Apparatus according to claim 11 wherein said flameholder is ofgenerally airfoil cross-section and includes a pivotable door memberattached to the side thereof away from said passage concave wall andpivotable between a first nonafterbuming position wherein it cooperateswith the remainder of the flameholder member to define an airfoilcrosssection and a second, afterburning position where it extends intothe passage to increase the size of the stagnation zone.

13. Apparatus according to claim 12 wherein said door member isperforated.

14. Apparatus according to claim 13 and including trigger means locatedon said door member to physically disturb the interface between thepilot products of combustion and the fuel-fluid mixture.

15. Apparatus according to claim 11 wherein said fuel injection meanscomprise a plurality or radially extending spray bars located in saidafterburner chamber upstream of said passage.

16. Apparatus according to claim 11 wherein said fuel injection meanscomprises conduit defining means positioned in the flameholder andshaped to communicate with said passage through a series of spacedapertures.

17. Apparatus according to claim 11 wherein said fuel injection meanscomprises conduit defining means extending radially in each vane andincluding a radially extending pattern of apertures opening into saidpassage through said convex wall.

18. Apparatus according to claim 11 and including flame-spreader meansinterconnecting said flameholder means.

19. Apparatus according to claim 11 and including diffuser meansupstream of said flameholders and vanes in said afterburner chamber toreduce the axial velocity but not the spin velocity of the swirlingfluid passing through the afterburner chamber.

20. Apparatus according to claim 11 wherein said flameholder means isspaced from said convex wall so that a cooling fuel-fluid mixture passestherealong and is positioned in closely spaced relation to said concavewall so that cooling fuel-air mixture is metered therebetween to pass athigh velocity along said con- 5 cave wall.

21. An afterburning having:

A. an afterburner duct having an axis and defining an afterburnerchamber therewithin,

B. means to pass fluid of density p through said afterburner chamber ina swirling flow pattern with tangential velocity V C. a cascade ofradially extending, airfoil shaped vanes each having a convex side and aconcave side said vanes being positioned concentrically about said axiswithin said afterburner chamber with the vanes shaped so that adjacentvanes define a passage therebetween which has an upstream portion whichdefines a passage which is in substantial alignment with the directionof fluid flow passing through the afterburner chamber and which has adownstream portion which defines a passage substantially in alignmentwith the axis so that the vanes serve as straightening vanes for thefluid flowing therebetween, and so that the concave side and the convexside of adjacent vanes form concave and convex walls of said passage,respectively,

D. a radially extending flameholder member positioned at each passageupstream portion adjacent the passage concave wall so as to establish astagnation zone downstream thereof in said passage adjacent said concavewall,

E. means to pass fuel into said passage to form a fuelfluid mixturepassing over said flameholder,

F. means to ignite said fuel-fluid mixture to establish pilot combustionin said stagnation zone within said passage adjacent said concave wallwith the products of combustion having a density p andtangentialvelocity V wherein p V, p V to establish outside-inside burning withinsaid passage progressing in the direction from the concave wall to theconvex wall.

22. An afterburner having:

A. an afterburner duct having an axis and defining an afterburnerchamber therewithin,

B. means to pass fluid of density p, through said afterburner chamber ina swirling flow pattern with a tangential velocity V C. a cascade ofradially extending, airfoil shaped vanes each having a convex side and aconcave side said vanes being positioned concentrically about said axiswithin said afterburner chamber with the vanes shaped so that adjacentvanes define a passage therebetween which has an upstream portion whichdefines a passage which is in substantial alignment with the directionof fluid flow passing through the afterburner chamber and which has adownstream portion which defines a passage substantially in alignmentwith the axis so that the vanes serve as straightening vanes for thefluid flowing therebetween, and so that the concave side and the convexside of adjacent vanes form concave and convex walls of said passage,respectively,

D. a flameholder member connected to the leading edge of each vane andprojecting therefrom into said passage to define a stagnation zonedownstream thereof.

23. Apparatus according to claim 22 wherein said flame holder member isa flat, perforated member.

24. Apparatus according to claim 1 wherein said flameholder membercomprises a radially extending hollow duct of airfoil cross-sectionpositioned upstream of and interdigitated between each adjacent vane andhaving aperture means in at least one wall of the trailing edge thereoforiented substantially laterally, and including means to pass afuel-rich, heated, fuel-air mixture through said flameholder to bedischarged substantially laterally therefrom through said apertures toignite upstream of said passage when brought into contact with saidfuel-air mixture to serve as a pilot flame to establish combustion inthe fluid-mixture passing through each passage of said vane cascade.

25. Apparatus according to claim 1 wherein said flameholder membercomprises a radially extending hollow duct of airfoil cross-sectionpositioned upstream of and interdigitated between each adjacent vane andhaving aperture means in at least one wall of the trailing edge thereoforiented substantially laterally, and including means to pass fuelthrough said flameholder to be discharged substantially laterallytherefrom through said apertures to be ignited upstream of said passagesto serve as a pilot flame to establish combustion in the fuel-fluidmixture passing through each passage of said vane cascade.

26. Apparatus according to claim 24 wherein said aperture pattern islocated in both walls of the flameholder member on opposite sides of thetrailing edge thereof to establish an enlarged pilot combustion zonedownstream thereof.

27. In an afterburner having an axis:

A. an afterburner casing concentric about the axis and defining anafterburner chamber therewithin,

B. a cascade of radially extending, airfoil shaped vanes each having aconvex side and a concave side said vanes being positionedcircumferentially within said afterburner combustion chamber and shapedto define passages therebetween with the concave surface of each vanedefining a concave wall of said passage and the convex surface of thevane defining a convex wall of said passage and with said vanes soshaped and oriented that the inlet portion of said passages extends inthe direction of fluid flow through the afterburner and the outletportion of said passage extends in the direction of the axis so that thevanes serve as fluid straightening vanes,

C. means to pass fluid through said afterburner chamber to establish atangential velocity so that the fluid enters the passage substantiallyin alignment with the direction of the passage inlet,

D. means to inject fuel into said fluid upstream of said vanes toestablish a fuel-fluid mixture passing through said passages.

E. flameholder means in the form of radially extending hollow members ofairfoil cross-section interdigitated between said vanes and positionedbetween said fuel injection means and said vane inlet and having aplurality of apertures at the trailing edge thereof extendingsubstantially normal to the direction of fluid flow, and

F. means to inject a hot, fuel-rich, fuel-fluid mixture into said hollowflameholder means and through said apertures substantially normally tosaid direction of fluid flow so as to ignite when coming in contacttherewith to establish a combustion pilot flame downstream of saidflameholder members and into said passage to establish combustion ofsaid fuel-fluid mixture in said passage.

28. Apparatus according to claim 27 wherein the density of thefuel-fluid mixture is p and its tangential velocity is V11, and further,wherein the density of the products of combustion of the pilot flame isp and its tangential velocity is V and wherein product parameter P1 11P2 12 29. Apparatus according to claim 27 and including trigger meansassociated with said flameholder means to physically disturb theinterface between said pilot flame products of combustion and saidfuel-fluid mixture.

30. Apparatus according to claim 29 wherein said trigger means comprisesan interrupted aperture pattern at the trailing edge of said flameholdermeans.

31. Apparatus according to claim 29 wherein said trigger means comprisesat least one projection or indentation in the trailing edge of theflameholder means.

32. Apparatus according to claim 16 wherein said vanes are ofsubstantially hollow construction and have an open radially outer endwhich is of minimal radial distance from the axis at the vane leadingedge and maximum radial distance from the axis at the vane trailing edgeand including:

A. means to cool vanes including:

1. means to pass a coolant along the outer periphery of said afterburnerchamber at a location to be intercepted by the hollow ends of saidvanes,

2. a plurality of flow turning vanes positioned across the open outerends of each of said hollow vanes and shaped to define passagestherebetween which intercept said coolant and change the direction offlow thereof into the hollow interior of said vanes,

3. means to discharge said coolant flow into said afterburner chamber ata station of lesser radius than the vane open outer end.

33. Apparatus according to claim 32 and wherein said vanes overlapcircumferentially. v

34. Apparatus according to claim 32 wherein said hollow vanes have aconcave wall and a convex wall and with said, concave wall facinggenerally in a downstream direction and wherein each vane also has:

A. a coolant inflow manifold extending across the opened outer end ofsaid vane to collect all coolant flow entering said vane,

B. a coolant outlet manifold located at a blade inner radial station,

C. a separator member attached to the interior of the blade leading edgeand the interior of the blade trailing edge and extending therebetweenand between the coolant inlet manifold and the coolant outlet manifoldto divide the interior of the blade into two parallel, radially directedpassages, and wherein said separator member is located closer to saidconvex wall than said concave passage extending between the coolantinlet and outlet manifold and with the separator member and the vaneconvex wall defining the boundaries thereof, and further wherein saidsecond parallel coolant passage extends between said coolant inlet andoutlet manifolds and is defined between said blade concave wall and saidseparator means which define closely spaced walls and having:

1. a corrugated member extending between said concave wall and saidseparator means with the corrugations thereof extending substantially ina radial direction so as to cause the coolant flow to scrub against saidconcave wall,

D. a plurality of said discharge slots located in said coolant outletmanifold to discharge said coolant into said afterburner chamber.

35. Apparatus according to claim 32 and having an inner body of generalcircular cross-section positioned concentrically about said axis, beinghollow in construction and connected to the inner radial end of each ofsaid vanes with the vane interiors being in communication with theinterior of inner body, said body having at least one slot in the wallthereof and wherein said hollow vanes have a concave wall and a convexwall and with said concave wall facing generally in a downstreamdirection so that all coolant flow passing through said vanes and intosaid inner body are discharged into said afterburner chamber throughsaid slots.

36. Apparatus according to claim 35 and including separator means in theinterior of each vane selectively shaped to control the amount ofcoolant flow which flows along the interior of said concave and saidconvex walls.

37. An annular combustion chamber having an axis and having:

A. coannular duct members concentric about said axis and defining anannular chamber therebetween,

B. means to pass fluid through said annular chamber in a swirling flowpattern,

C. a cascade of radially extending, airfoil shaped vanes each having aconvex side and a concave side said vanes being positionedconcentrically about said axis within said annular chamber with thevanes shaped so that adjacent vanes define a passage therebetween whichhas an upstream portion which defines a passage which is in substantialalignment with the direction of fluid flow passing through the annularchamber and whichhas a downstream portion which defines a passagesubstantially in alignment with the axis so that the vanes serve asstraightening vanes for the fluid flowing therebetween, and so that theconcave side and convex side of adjacent vanes form concave and convexwalls of said passage, respectively, and with the vanes being shaped sothat said concave and convex walls of each passage are positionedsubstantially about a common center of curvature.

D. a flameholder member positioned and shaped to establish a stagnationzone downstream thereof in said passage adjacent said concave wall,

E. means to pass fuel into said passage to form a swirling fuel-fluidmixture passing over said flameholder, and

' F. means to ignite said fuel-fluid mixture to establish combustion insaid zone within said passage adjacent said concave wall to establishoutside-inside burning within said passage progressing in the directionfrom the concave wall to the convex wall.

38. Apparatus according to claim 37 and including means to cool saidvanes.

39. Apparatus according to claim 37 wherein said flameholder member is aradially extending perforated plate member pivotally attached to theleading edge of each vane and pivotally between an operative positionwherein it cooperates with the vane concave wall to define thestagnation zone and a retracted position wherein it substantially abutsthe vane concave wall.

40. Apparatus according to claim 37 wherein said flameholder member is aradially extending member of airfoil cross-section positioned at theinlet of said passage adjacent each vane concave wall and selectivelyshaped therefrom to define a cooling fluid metering passage therebetweenand having a fixed portion and a movable portion wherein said movableportion comprises:

A. a radially extending and perforated plate member pivotally attachedto the flameholder fixed portion and pivotally between an operableposition wherein it cooperates with the flameholder fixed portion todefine said stagnation zone downstream thereof and a retracted positionwherein it cooperates with said fixed portion in defining a radiallyextending member in airfoil cross-section.

41. Apparatus according to claim 37 wherein said fluid passing means isa concentric mixer comprising:

A. a first duct of substantially circular cross-section supportedconcentrically about said axis and defining a first passage therewith ascommunicating between said mixer and said annular combustion chamber, asecond duct. enveloped within said first duct and being of substantiallycircular cross-section and concentric therewith so as to cooperate withsaid first duct in defining an annular passage therebetween and so as todefine a second passage therewithin, means to pass first swirling streamof a first fluid of density p, and tangential velocity V through saidsecond passage into said first passage to establish a product parameterp, V means to pass a second swirling fluid stream through said mixerannular passage into said first passage 'to establish an interfacebetween said swirling fluids and with the second fluid being of densityp and tangential velocity V to establish a product parameter p V whichis less than the product parameter p, V to accelerate mixing betweensaid first and second fluids.

42. Apparatus according'to claim 37 wherein said fluid passing means isa barberpole mixer positioned upstream of said annular combustionchamber and including:

A. an inner duct concentric about said axis to define a first passagetherewithin,

B. a second duct concentrically enveloping said first duct andcooperating therewith to define an annular passage therebetween,

C. means connecting said second duct to the outer coannular duct of saidannular combustion chamber,

D. a conical separator duct extending between said first and secondducts and having an upstream end connected to said first duct and adownstream end connected to said second duct, and having:

1. a plurality of slots located circumferentially thereabout and eachbeing disposed helically with respect to said axis and of selectednumber,

size and spacing to define the total slot area and with said total areaof the slots being a function of the cross-sectional area of the firstpassage,

2. a scoop member enveloping each slot,

E. means to pass a first swirling fluid through said first passage and asecond fluid through said slots to'mix as a swirling flow mixture insaid connecting means.

43. An afterburner having:

A. an afterburner duct having an axis and defining an afterburnerchamber therewithin,

B. means to pass a fuel-fluid mixture through said afterburner chamberin a selected swirling flow pattern,

C. a cascade of radially extending, airfoil shaped vanes each having aconvex side and a concave side said vanes being positionedconcentrically about said axis within said afterburner chamber with thevanes shaped so that adjacent vanes define a passage therebetween whichhas an upstream portion which defines a passage which is in substantialalignment with the direction of the fuel-fluid mixture flow passingthrough the afterburner chamber and which has a downstream portion whichdefines a passage substantially in alignment with the axis so that thevanes serve as straightening vanes for the fluid flowing therebetween,and so that the concave side and convex side of adjacent vanes formconcave and convex walls of said passage, respectively, and with saidvanes shaped so that the concave and convex walls of each passage havesubstantially a common center of curvature,

portion thereof, and including means to pass cooling fluid through theinterior of said vanes for discharge through said apertures.

46. Apparatus according to claim 43 wherein said vanes are hollow andincluding a hollow'inner body positioned concentrically within saidafterburner duct and said cascade of vanes to cooperate with said ductin defining an annular passage in which said vanes are located, saidinner body having discharge slots forward of said vanes, and means topass coolant flow through said vanes into said inner body and out ofsaid discharge slot.

ggs UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pateht3,701,255 i Dated October 31, 1972.

Inventor(s) Stanley J Markowski It is certified that error appears inthe above-identified patent and that said Letters Patent are'herebycorrected as shown below:

Claim 32, line -1 Delete "16" and insert --l Signed and sealed this 13thda'y of March 1973.

(SEAL)- Attest: v

EDWARD M.FLETCHER,JR ROBERT GOTTSCHALK Attesting Officer Commissioner ofPatents

1. An afterburner having: A. an afterburner duct having an axis anddefining an afterburner chamber therewithin, B. means to pass fluidthrough said afterburner chamber in a swirling flow pattern, C. acascade of radially extending, airfoil shaped vanes each having a convexside and concave side, said vane positioned concentrically about saidaxis within said afterburner chamber with the vanes shaped so thatadjacent vanes define a passage therebetween which has an upstreamportion which defines a passage which is in substantial alignment withthe direction of fluid flow passing through the afterburner chamber andwhich has a downstream portion which defines a passage substantially inalignment with the axis so that the vanes serve as straightening vanesfor the fluid flowing therebetween, and so that the concave side andconvex side of adjacent vanes form concave and convex walls of saidpassage, respectively, D. a radially extending flameholder memberpositioned at each passage upstream portion adjacent the passage concavewall so as to establish a stagnation zone downstream thereof in saidpassage adjacent said concave wall, E. means to pass fuel into saidpassage to form a fuel-fluid mixture passing over said flameholder, F.means to ignite said fuel-fluid mixture to establish combustion in saidzone within said passage adjacent said concave wall to establishoutside-inside burning within said passage progressing in the directionfrom the concave wall to the convex wall.
 2. a plurality of flow turningvanes positioned across the open outer ends of each of said hollow vanesand shaped to define passages therebetween which intercept said coolantand change the direction of flow thereof into the hollow interior ofsaid vanes,
 2. Apparatus according to claim 1 wherein said flameholdermember is of generally airfoil cross-section and includes a pivotabledoor member attached to the side thereof away from said passage concavewall and pivotable between a first non-afterburning position wherein itcooperates with the remainder of the flameholder member to define anairfoil cross-section and a second, afterburning position where itextends into the passage to increase the size of the stagnation zone. 2.a scoop member enveloping each slot, E. means to pass a first swirlingfluid through said first passage and a second fluid through said slotsto mix as a swirling flow mixture in said connecting means.
 3. means todischarge said coolant flow into said afterburner chamber at a stationof lesser radius than the vane open outer end.
 3. Apparatus according toclaim 2 wherein said door member is perforated.
 4. Apparatus accordingto claim 3 and including trigger means located on said door member tophysically disturb the interface between the products of combustion ofthe stagnation zone and the fuel-fluid mixture.
 5. Apparatus accordingto claim 1 wherein said fuel injection means comprises a plurality ofradially extending spray bars located in said afterburner chamberupstream of said passage.
 6. Apparatus according to claim 1 wherein saidfuel injection means comprises conduit defining means positioned in theflameholder means and shaped to communicate with said passage through aseries of spaced apertures.
 7. Apparatus according to claim 1 whereinsaid fuel injection means comprises conduit defining means extendingradially in each vane and including a radially extending pattern ofapertures opening into said passage through said concave wall. 8.Apparatus according to claim 1 and including flamespreader meansinterconnecting said flameholder means.
 9. Apparatus according to claim1 and including diffuser means upstream of said flameholder and vanes insaid afterburner chamber to reduce the axial velocity but not the spinvelocity of the swirling fluid passing through the afterburner chamber.10. Apparatus according to claim 1 wherein said flameholder means isspaced from said convex wall so that a cooling fuel-fluid mixture passestherealong and is positioned in closely spaced relation to said concavewall so that cooling fuel-fluid mixture is metered therebetween to passat high velocity along said concave wall.
 11. An afterburner having anaxis and including: A. an afterburner case concentric about the axis,and defining an afterburner chamber therewithin, B. a plurality ofradially directed, circumferentially oriented vanes each having a convexside and concave side, said vanes forming a vane cascade extendingacross at least a part of said afterburner chamber, wherein said vanesare airfoil shaped such that adjacent vanes define a passage andcombustor therebetween with the concave side of one vane forming aconcave wall of the passage and the convex side of the adjacent vaneforming a convex wall of the passage, and such vanes being selectivelyshaped so as to define the inlet portion of said passage to extendsubstantially in the direction of intended fluid flow and the outletportion of passage extending substantially along said axis, C. aradially extending flameholder of airfoil cross-section positionedadjacent but in spaced relationship to the concave wall of said passageat the inlet portion thereof to define a metering passage for coolingfluid between said flameholder and said concave wall, D. means to passfluid through said afterburner, E. means to inject fuel into said fluidupstream of said passage, F. means to ignite said fuel-fluid mixturedownstream of said flameholders to establish pilot combustion in thestagnation zone formed downstream thereof so that the products ofcombustion have a density, Rho 1, and a tangential velocity Vt1, and sothat the unvitiated fuel-fluid mixture has a density, Rho 2, andtangential velocity Vt2 to establish the product parameter ratio Rho 1Vt12> Rho 2 Vt22 to thereby accelerate intermixing and combustionbetween the unvitiated fuel-fluid mixture and the pilot products ofcombustion.
 12. Apparatus according to claim 11 wherein said flameholderis of generally airfoil cross-section and includes a pivotable doormember attached to the side thereof away from said passage concave walland pivotable between a first nonafterburning position wherein itcooperates with the remainder of the flameholder member to define anairfoil cross-section and a second, afterburning position where itextends into the passage to increase the size of the stagnation zone.13. Apparatus according to claim 12 wherein said door member isperforated.
 14. Apparatus according to claim 13 and including triggermeans located on said door member to physically disturb the interfacebetween the pilot products of combustion and the fuel-fluid mixture. 15.Apparatus according to claim 11 wherein said fuel injection meanscomprise a plurality or radially extending spray bars located in saidafterburner chamber upstream of said passage.
 16. Apparatus according toclaim 11 wherein said fuel injection means comprises conduit definingmeans pOsitioned in the flameholder and shaped to communicate with saidpassage through a series of spaced apertures.
 17. Apparatus according toclaim 11 wherein said fuel injection means comprises conduit definingmeans extending radially in each vane and including a radially extendingpattern of apertures opening into said passage through said convex wall.18. Apparatus according to claim 11 and including flame-spreader meansinterconnecting said flameholder means.
 19. Apparatus according to claim11 and including diffuser means upstream of said flameholders and vanesin said afterburner chamber to reduce the axial velocity but not thespin velocity of the swirling fluid passing through the afterburnerchamber.
 20. Apparatus according to claim 11 wherein said flameholdermeans is spaced from said convex wall so that a cooling fuel-fluidmixture passes therealong and is positioned in closely spaced relationto said concave wall so that cooling fuel-air mixture is meteredtherebetween to pass at high velocity along said concave wall.
 21. Anafterburning having: A. an afterburner duct having an axis and definingan afterburner chamber therewithin, B. means to pass fluid of densityRho 1 through said afterburner chamber in a swirling flow pattern withtangential velocity Vt1, C. a cascade of radially extending, airfoilshaped vanes each having a convex side and a concave side said vanesbeing positioned concentrically about said axis within said afterburnerchamber with the vanes shaped so that adjacent vanes define a passagetherebetween which has an upstream portion which defines a passage whichis in substantial alignment with the direction of fluid flow passingthrough the afterburner chamber and which has a downstream portion whichdefines a passage substantially in alignment with the axis so that thevanes serve as straightening vanes for the fluid flowing therebetween,and so that the concave side and the convex side of adjacent vanes formconcave and convex walls of said passage, respectively, D. a radiallyextending flameholder member positioned at each passage upstream portionadjacent the passage concave wall so as to establish a stagnation zonedownstream thereof in said passage adjacent said concave wall, E. meansto pass fuel into said passage to form a fuel-fluid mixture passing oversaid flameholder, F. means to ignite said fuel-fluid mixture toestablish pilot combustion in said stagnation zone within said passageadjacent said concave wall with the products of combustion having adensity Rho 2 and tangential velocity Vt2 wherein Rho 1 Vt1> Rho 2 Vt2to establish outside-inside burning within said passage progressing inthe direction from the concave wall to the convex wall.
 22. Anafterburner having: A. an afterburner duct having an axis and definingan afterburner chamber therewithin, B. means to pass fluid of densityRho 1 through said afterburner chamber in a swirling flow pattern with atangential velocity Vti, C. a cascade of radially extending, airfoilshaped vanes each having a convex side and a concave side said vanesbeing positioned concentrically about said axis within said afterburnerchamber with the vanes shaped so that adjacent vanes define a passagetherebetween which has an upstream portion which defines a passage whichis in substantial alignment with the direction of fluid flow passingthrough the afterburner chamber and which has a downstream portion whichdefines a passage substantially in alignment with the axis so that thevanes serve as straightening vanes for the fluid flowing therebetween,and so that the concave side and the convex side of adjacent vanes formconcave and convex walls of said passage, respectively, D. a flameholdermember connected to the leading edge of each vane and projectingtherefrom into said passage to define a stagnation zone downstreamthereof.
 23. Apparatus according to claim 22 wherein said flame holdermember is a flat, perforated member.
 24. Apparatus according to claim 1wherein said flameholder member comprises a radially extending hollowduct of airfoil cross-section positioned upstream of and interdigitatedbetween each adjacent vane and having aperture means in at least onewall of the trailing edge thereof oriented substantially laterally, andincluding means to pass a fuel-rich, heated, fuel-air mixture throughsaid flameholder to be discharged substantially laterally therefromthrough said apertures to ignite upstream of said passage when broughtinto contact with said fuel-air mixture to serve as a pilot flame toestablish combustion in the fluid-mixture passing through each passageof said vane cascade.
 25. Apparatus according to claim 1 wherein saidflameholder member comprises a radially extending hollow duct of airfoilcross-section positioned upstream of and interdigitated between eachadjacent vane and having aperture means in at least one wall of thetrailing edge thereof oriented substantially laterally, and includingmeans to pass fuel through said flameholder to be dischargedsubstantially laterally therefrom through said apertures to be ignitedupstream of said passages to serve as a pilot flame to establishcombustion in the fuel-fluid mixture passing through each passage ofsaid vane cascade.
 26. Apparatus according to claim 24 wherein saidaperture pattern is located in both walls of the flameholder member onopposite sides of the trailing edge thereof to establish an enlargedpilot combustion zone downstream thereof.
 27. In an afterburner havingan axis: A. an afterburner casing concentric about the axis and definingan afterburner chamber therewithin, B. a cascade of radially extending,airfoil shaped vanes each having a convex side and a concave side saidvanes being positioned circumferentially within said afterburnercombustion chamber and shaped to define passages therebetween with theconcave surface of each vane defining a concave wall of said passage andthe convex surface of the vane defining a convex wall of said passageand with said vanes so shaped and oriented that the inlet portion ofsaid passages extends in the direction of fluid flow through theafterburner and the outlet portion of said passage extends in thedirection of the axis so that the vanes serve as fluid straighteningvanes, C. means to pass fluid through said afterburner chamber toestablish a tangential velocity so that the fluid enters the passagesubstantially in alignment with the direction of the passage inlet, D.means to inject fuel into said fluid upstream of said vanes to establisha fuel-fluid mixture passing through said passages, E. flameholder meansin the form of radially extending hollow members of airfoilcross-section interdigitated between said vanes and positioned betweensaid fuel injection means and said vane inlet and having a plurality ofapertures at the trailing edge thereof extending substantially normal tothe direction of fluid flow, and F. means to inject a hot, fuel-rich,fuel-fluid mixture into said hollow flameholder means and through saidapertures substantially normally to said direction of fluid flow so asto ignite when coming in contact therewith to establish a combustionpilot flame downstream of said flameholder members and into said passageto establish combustion of said fuel-fluid mixture in said passage. 28.Apparatus according to claim 27 wherein the density of the fuel-fluidmixture is Rho 1 and its tangential velocity is Vtl, and further,wherein the density of the products of combustion of the pilot flame isRho 2 and its tangential velocity is Vt2 and wherein product parameterRho 1 Vt12 > Rho 2 Vt22.
 29. Apparatus according to claim 27 andincluding trigger means associated with said flameholder means tophysically disturb the iNterface between said pilot flame products ofcombustion and said fuel-fluid mixture.
 30. Apparatus according to claim29 wherein said trigger means comprises an interrupted aperture patternat the trailing edge of said flameholder means.
 31. Apparatus accordingto claim 29 wherein said trigger means comprises at least one projectionor indentation in the trailing edge of the flameholder means. 32.Apparatus according to claim 16 wherein said vanes are of substantiallyhollow construction and have an open radially outer end which is ofminimal radial distance from the axis at the vane leading edge andmaximum radial distance from the axis at the vane trailing edge andincluding: A. means to cool vanes including:
 33. Apparatus according toclaim 32 and wherein said vanes overlap circumferentially.
 34. Apparatusaccording to claim 32 wherein said hollow vanes have a concave wall anda convex wall and with said concave wall facing generally in adownstream direction and wherein each vane also has: A. a coolant inflowmanifold extending across the opened outer end of said vane to collectall coolant flow entering said vane, B. a coolant outlet manifoldlocated at a blade inner radial station, C. a separator member attachedto the interior of the blade leading edge and the interior of the bladetrailing edge and extending therebetween and between the coolant inletmanifold and the coolant outlet manifold to divide the interior of theblade into two parallel, radially directed passages, and wherein saidseparator member is located closer to said convex wall than said concavepassage extending between the coolant inlet and outlet manifold and withthe separator member and the vane convex wall defining the boundariesthereof, and further wherein said second parallel coolant passageextends between said coolant inlet and outlet manifolds and is definedbetween said blade concave wall and said separator means which defineclosely spaced walls and having:
 35. Apparatus according to claim 32 andhaving an inner body of general circular cross-section positionedconcentrically about said axis, being hollow in construction andconnected to the inner radial end of each of said vanes with the vaneinteriors being in communication with the interior of inner body, saidbody having at least one slot in the wall thereof and wherein saidhollow vanes have a concave wall and a convex wall and with said concavewall facing generally in a downstream direction so that all coolant flowpassing through said vanes and into said inner body are discharged intosaid afterburner chamber through said slots.
 36. Apparatus according toclaim 35 and including separator means in the interior of each vaneselectively shaped to control the amount of coolant flow which flowsalong the interior of said concave and said convex walls.
 37. An annularcombustion chamber having an axis and having: A. coannular duct membersconcentric about said axis and defining an annular chamber therebetween,B. means to pass fluid tHrough said annular chamber in a swirling flowpattern, C. a cascade of radially extending, airfoil shaped vanes eachhaving a convex side and a concave side said vanes being positionedconcentrically about said axis within said annular chamber with thevanes shaped so that adjacent vanes define a passage therebetween whichhas an upstream portion which defines a passage which is in substantialalignment with the direction of fluid flow passing through the annularchamber and which has a downstream portion which defines a passagesubstantially in alignment with the axis so that the vanes serve asstraightening vanes for the fluid flowing therebetween, and so that theconcave side and convex side of adjacent vanes form concave and convexwalls of said passage, respectively, and with the vanes being shaped sothat said concave and convex walls of each passage are positionedsubstantially about a common center of curvature. D. a flameholdermember positioned and shaped to establish a stagnation zone downstreamthereof in said passage adjacent said concave wall, E. means to passfuel into said passage to form a swirling fuel-fluid mixture passingover said flameholder, and F. means to ignite said fuel-fluid mixture toestablish combustion in said zone within said passage adjacent saidconcave wall to establish outside-inside burning within said passageprogressing in the direction from the concave wall to the convex wall.38. Apparatus according to claim 37 and including means to cool saidvanes.
 39. Apparatus according to claim 37 wherein said flameholdermember is a radially extending perforated plate member pivotallyattached to the leading edge of each vane and pivotally between anoperative position wherein it cooperates with the vane concave wall todefine the stagnation zone and a retracted position wherein itsubstantially abuts the vane concave wall.
 40. Apparatus according toclaim 37 wherein said flameholder member is a radially extending memberof airfoil cross-section positioned at the inlet of said passageadjacent each vane concave wall and selectively shaped therefrom todefine a cooling fluid metering passage therebetween and having a fixedportion and a movable portion wherein said movable portion comprises: A.a radially extending and perforated plate member pivotally attached tothe flameholder fixed portion and pivotally between an operable positionwherein it cooperates with the flameholder fixed portion to define saidstagnation zone downstream thereof and a retracted position wherein itcooperates with said fixed portion in defining a radially extendingmember in airfoil cross-section.
 41. Apparatus according to claim 37wherein said fluid passing means is a concentric mixer comprising: A. afirst duct of substantially circular cross-section supportedconcentrically about said axis and defining a first passage therewith ascommunicating between said mixer and said annular combustion chamber, asecond duct enveloped within said first duct and being of substantiallycircular cross-section and concentric therewith so as to cooperate withsaid first duct in defining an annular passage therebetween and so as todefine a second passage therewithin, means to pass first swirling streamof a first fluid of density Rho 1 and tangential velocity Vt1 throughsaid second passage into said first passage to establish a productparameter Rho 1 Vt12, means to pass a second swirling fluid streamthrough said mixer annular passage into said first passage to establishan interface between said swirling fluids and with the second fluidbeing of density Rho 2 and tangential velocity Vt2 to establish aproduct parameter Rho 2 Vt22 which is less than the product parameterRho 1 Vt12 to accelerate mixing between said first and second fluids.42. Apparatus according to claim 37 wherein said fluid passing means isa barberpole mixer pOsitioned upstream of said annular combustionchamber and including: A. an inner duct concentric about said axis todefine a first passage therewithin, B. a second duct concentricallyenveloping said first duct and cooperating therewith to define anannular passage therebetween, C. means connecting said second duct tothe outer coannular duct of said annular combustion chamber, D. aconical separator duct extending between said first and second ducts andhaving an upstream end connected to said first duct and a downstream endconnected to said second duct, and having:
 43. An afterburner having: A.an afterburner duct having an axis and defining an afterburner chambertherewithin, B. means to pass a fuel-fluid mixture through saidafterburner chamber in a selected swirling flow pattern, C. a cascade ofradially extending, airfoil shaped vanes each having a convex side and aconcave side said vanes being positioned concentrically about said axiswithin said afterburner chamber with the vanes shaped so that adjacentvanes define a passage therebetween which has an upstream portion whichdefines a passage which is in substantial alignment with the directionof the fuel-fluid mixture flow passing through the afterburner chamberand which has a downstream portion which defines a passage substantiallyin alignment with the axis so that the vanes serve as straighteningvanes for the fluid flowing therebetween, and so that the concave sideand convex side of adjacent vanes form concave and convex walls of saidpassage, respectively, and with said vanes shaped so that the concaveand convex walls of each passage have substantially a common center ofcurvature, D. flameholder means shaped and positioned to establish astagnation zone in said passage adjacent said concave wall, E. means toignite said fuel-fluid mixture to establish combustion in said zonewithin said passage adjacent said concave wall to establishoutside-inside burning within said passage progressing in the directionfrom the concave wall to the convex wall.
 44. Apparatus according toclaim 43 and including means to cool said vanes.
 45. Apparatus accordingto claim 43 wherein said vanes are hollow and include at least oneaperture near the radially inner end thereof and toward the forwardportion thereof, and including means to pass cooling fluid through theinterior of said vanes for discharge through said apertures. 46.Apparatus according to claim 43 wherein said vanes are hollow andincluding a hollow inner body positioned concentrically within saidafterburner duct and said cascade of vanes to cooperate with said ductin defining an annular passage in which said vanes are located, saidinner body having discharge slots forward of said vanes, and means topass coolant flow through said vanes into said inner body and out ofsaid discharge slot.